Volume 20, Number 3
July 2004
AQUATIC MATING STRATEGIES OF THE MALE PACIFIC HARBOR SEAL (PHOCA VITULINA
RICHARDII):
ARE MALES DEFENDING THE HOTSPOT?
Sean A. Hayes, Daniel P. Costa, James T. Harvey, and Burney J. Le Boeuf
ABSTRACT
Compared to the harem and resource defense systems of terrestrial mating
pinnipeds,
males of aquatic mating species appear unable to monopolize females or
resources. We
investigated movements, acoustics, and aquatic territorial behavior of male
harbor
seals, Phoca vitulina richardii, in Elkhorn Slough, California, using VHF
telemetry,
hydrophones, and acoustic playback experiments. During the mating season 22
males
increased time spent in the water and away from haul-out locations, exhibiting
activity patterns similar to Atlantic subspecies. Two acoustic display
patterns were
observed. At one location multiple males aggregated to display with acoustic
activity
peaking one month before peak estrus. At two other locations, lone males
displayed
primarily during peak estrus. Acoustic display areas were non-adjacent with a
mean ±
SE size of 4,228 ± 576 m2, similar to harbor seal display patterns in the
Moray Firth,
Scotland. Underwater playbacks of male vocalizations were used to!
define territorial boundaries by inducing responses from territory-holding
males.
Four solitary males defended adjacent territories (mean area 39,571 ± 18,818
m2) along
a travel corridor, similar to observations of harbor seals at Miquelon,
Newfoundland.
Acoustic display stations appeared to be subcomponents of larger territories.
Males
exhibited site fidelity to territories for at least 2-4 yr. Females moved
through
territories freely. The establishment of male-display territories along
female-traffic
corridors resembles terrestrial systems described as hotspot leks.
Keywords: aquatic mating system, breeding behavior, hotspot lek, harbor seal,
Phoca
vitulina, pinniped.
© Copyright by The Society for Marine Mammalogy 2004
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